Separation membranes are classified into micro-filtration (MF) membranes, ultra-filtration (UF) membranes, nano-filtration (NF) membranes, reverse osmosis (RO) membranes, and the like, according to a pore size thereof. Meanwhile, the reverse osmosis membrane, a type of semipermeable membrane, may remove salts from brackish water, sea water and the like, using a principle of causing a solution and a solute to be separated in predetermined directions when an aqueous solution having salts dissolved therein is pressurized in one direction, thereby being able to be used to desalinate a great quantity of water for industrial, agricultural, domestic and other purposes, into relatively lower-salinity water.
More specifically, brackish and sea water desalination processes using the reverse osmosis membrane refer to processes of filtering salts, ions or the like, dissolved in an aqueous solution through a reverse osmosis membrane and allowing refined water to pass through the membrane, when the reverse osmosis membrane passes through the aqueous solution having salts, ions or the like dissolved therein while pressure is applied to the aqueous solution. At this time, the level of applied pressure needs to be greater than that of osmotic pressure. Accordingly, osmotic pressure is higher in accordance with an increase in salinity of the aqueous solution and consequently, the pressure required to be applied to supply water may be increased, causing the depletion of a greater amount of energy.
Thus, in order to desalinate brackish water, sea water and the like, containing a great deal of salts, a reverse osmosis membrane needs to have properties allowing a great quantity of water to pass therethrough, even at relatively low pressure, that is, high permeate flux properties, as well as having salt removal capabilities.
Korean Patent Registration No. 0477590 (Oct. 5, 2000), relating to a method of manufacturing a reverse osmosis membrane with high flux, discloses a method of manufacturing a reverse osmosis membrane with high flux, the method being characterized in that a film formed through interfacial polymerization occurring on a surface of a support layer by bringing an organic solvent containing an amine reactive compound such as a polyfunctional acyl halide or the like and phosphinyl alkyl chloride dissolved therein into contact with the support layer, after coating at least one aqueous polyfunctional amine solution on the support layer and removing an excessive amount of the solution therefrom, is washed using an aqueous basic solution to thereby manufacture a reverse osmosis membrane. In the above related art, phosphinyl alkyl chloride is added at the time of the interfacial polymerization through which a polyamide active layer is formed, and the phosphinyl alkyl chloride may be involved in the interfacial polymerization and serve to densely form a fine surface structure while having high degrees of fluidity and integrity. However, although the related art has advantages of increasing a permeate flux, it has defects in that a predetermined level of a salt rejection rate may not be maintained and deviation thereof may be significant.
Meanwhile, Korean Patent Laid-Open Publication No. 1996-0013437 (May 22, 1996), relating to a method of manufacturing a reverse osmosis module housing having antibiosis, discloses a reverse osmosis module housing having improved bacteria removal capabilities and excellent antibiosis, the reverse osmosis module housing being manufactured by combining a module element formed by winding a complex semipermeable membrane including a porous support stacked on a non-woven polyester fabric and an active layer (a crosslinked polyamide ultrathin film) obtained by interfacially polymerizing a polyfunctional amine solution and a polyfunctional halide solution on the surface of the porous support, in a spiral wound manner, with a module housing fabricated by mixing a polypropylene resin and zeolite with a compound having silver and copper absorbed therein. However, the reverse osmosis module housing is formed by combining the module element obtained by winding the complex semipermeable membrane in the spiral wound manner, with the module housing including zeolite, and the reverse osmosis module housing is merely provided to improve antibiosis. Thus, the reverse osmosis module housing is not associated with a permeate flux and a salt rejection rate of the polyamide active layer. Further, a structure thereof is complex and thus, various fields of application thereof are restricted.
Thus, the present invention is provided by the applicant thereof as a result of repeated research in order to improve a permeate flux and a salt rejection rate of a reverse osmosis membrane.